Heat-treating furnace



,5 Sneetsneet 1 INVEAQTOR.

Oct.*16, 1945. F A, ENDREss HEAT'TREATNG FURNAGE Filed Dec. 2, 1941 Oct. 16, 1945. F. A, ENDREss HEAT TREATING FURNACE 5 Sheets-Sheet 3 Filed Dec.

1 ENTOR 11W/federn@ .T709

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I I l T" I 1 L- Patented Oct. 16, 1945 `llrederick En'tlress, Detroit, Mich., assignorfto :Tuir-.Hard Corporation, Detroit, Mich, .ia A:cor-

:poration fof Michigan Application December 2, 1941, seri.fn-rm. `421,362

invention ,relates 4to furnaces, and more ,particularly 'to means and -.`a .me`thod oi controlling the operation cfa ,furnace in `preparing same 'for subsequently heat treating a material. Al`referably thepresent invention is applicable "to a "furnace 'having a retort chamber f'or receiving the material to "be .treated `by radiant heat, the "retort 'chamber 'being `raised to the desired relatively high .temperatures by burning .a 'combustible "fuel in said retort chamber, and it. is .mnreespec'iallyuseful .for processing "ferrous materials las described and claimed in my cepend- Iing application .for patent, Ser. No. 370,577, filed 4December '118, '19140, ventitled lProcess `lfor iheat ytreatin-g `s'teeli 'in l1eat1treating, and especially heat treating materia'lsibyaprocess requiring very high tem- ;perature's, 'it :isnoted that these "high retort :temperatures can -only be 'had 'by means of a 'flame playing 'directly in the retort chamber. 'Ihe 'presence o'f oxygen in the retort chamber when Jthe `material yis being processed therein is in- 'urious tothe work, as iit causes V,oxidation and 'burning o'f the material'or Work. It is necessary, when employing high temperatures to `remove 'the *products `'of Ycombustion and to introduce an atmosphere "in said retort chamber suitable for use in subsequent operations of the process, the preferred process 4utilizing heat stored in fthe yre- "tort chamber. Furnaces of themufe ltype 'are unsuitable for use lin -a' Aprocess 'employing lthese excessively "high temperatures as itis impossible to obtain such temperatures Ain the' retort chamber 'and therefore vdirect heating of the retort -fchaniber isnecessary. VThe -products of combustvtionciif .left'inthe-retort chamber, Vare injurious Ato fthe Work fand also prevent' one :from vpreparing the proper 4atmosphere around lthe Work being processed v'in Vorder to eliminate oxidation hand burningfof-the work and the formation -o'f scale.

An Acbjectof my vpresent invention is 'to proc- 'ess material in a gaslfred ffurnace or-other similar furnaces "having -a vretort chamber, in which fa combustible fuel has `been burn-ed to 'heat the chamber to 'the temperature required, =and to inftroduce a. vga-s vatmosphere vinto "said 'chamber "whichlscavenges th'echamber of the products of -combustion,'and which then provides an atmosphere therein having ya `predetermined analysis .and pressure suitable ffor use in l'subsequent foperations of theffurnace in processing *the material whichisfto 'be treatedtherein.

Aurther-object of vmy invention :is lto accomlpli'sh these Vresul-ts automatically, preferably lby providing rmeans automatically operable 'to ysub- Iject 'the .'furnace pto 'a "plurality of successive -o p- 'erations which scavenges the furnace retort chamber oftheproducts ofcombustion and prepares an atmosphere therein of a predetermined analysis yandpressure 'suitable for use'in subsequent :operations of fthe furnace inprocess'ingthe `material which is to be heat 'treated therein.

Obviously, there maybe many means "for controllingthese `operations to which the furnace is subjected, land for purposes of illustration "1 lhave chosen ,to .illustrate Asome `of Ythe 'more'practicalmea-ns for accomplishing the desired result. Obviously,y lthe principles of ymy invention can `be *carried out by hand land ii'here'fore my inven- -itionm-aybe defined lby method or process claims las `Well as by claims broadly and specical'ly directed 'to the -means vfor carrying 'out rnyhovel -process Ior method.

"For a more 'detailedunderstanding of my iinverftion reference may "be had to the accompanying -rawings Vand description defi-ning pre- `'fer-red ern-booliments of l"my invention, in which like characters refer "tolike parts throughout 'the 'several lviews, `and vin which':

f-Fig. l is an elevational View of la preferred embodiment o'fmy invention, illustrating the v'iurnace-fcontrol 'meanssomewhat diagrammatically,

Fig. 2 is a diagrammatic View of a modified Ifurnace contr-o1 means,

Fig. B lis a-:detailsectionalviewof afurnace found to be Asuitable -fo=r my purpose and appli- -cable lfor -lm-y method -of operation,

`vtionfanti Fig. S5 .is @a t'ime diagram ofthe successive vsteps in my process of prepa-ring the retort chamber for carrying out subsequent operations -of fthe heat treating fprocess.

The :furnace it illustrated Yherein v`provides a retort chamber lf yinto vwhich afsupply vfof combustirble fuel:.rn'ixture i-s fed lby means "of 'a suitable induction system fl-I including fa main *fuel supply Yline i122 .controlled by 'a vmain""s`hu`t off yalye `:I-Z-l, :an .air l mixing 1device I'4 Vand a control ya'lve "t5, fromwhich lead the conduits 4-or Vpipes I6 which are preferably divided to form a rpai-ro'f .brancnconduits vHic and l|61; illeadingi-to the fur- Kna'ce,fuelfmixture,intake port openings .IL Preferably the conduits 15a, and it-b terminate iin fuel nozzles i8 which-directftheffuelimixture into rthe furnaceretortchamber 4,0, where same risrignited and .burned to heat :therafurnaceY .said heat-,being customarily stored in the ,retort Lchamber wa11s, the stored fheat being .subsequently `usedtc ,processthe ma'terial being treated.

door 25 which may be opened so that access may .1.'

be had to the interior of the retort chamber. Valve 21 is incorporated With the pipe or conduit 23 to control the flow of gas therethrough'. If

desired the second induction systemmay exhaust into conduits l5, and thus the flushing gas is introduced from pipe or conduit 23o: to branched pipes Ia and lh in the furnace as shovvn in Fig. 4.

In heat treating material in this furnace which maybe classified broadly as of the gas red type, thelfurnace" is heated to a relatively high temperature, and the direct llame in the retort chamber', is then cut off beforethe material being treated 'isplaced Within the retort chamber, said material` being brought to temperature by the storedr radiant heat.l

Mypresent inventionV isdirected 4to the means a'nfdmetltiodv for preparingthe `furnace retort chamber for subsequent operations in the heat treatment of material, particularly ferrous matelrials. YThis .is accomplished by rst burning a combustible fuel Within the furnace retort chamhber'to bring same up to temperature', and when the .furnace is at temperature to cut off the supply of combustibleY fuel being fed into the retort chamber. Next the valve 2 is opened wide and the flushing gas of predetermined analysis, suitable yfor"subseduent heat treatment of the mate- `rialbeingprocesseL is injected into the retort chamber to s'cavenge said chamber of the products ofcoinbustion which remain therein, after turning off the fuel supply. ,-Ifheproducts of combustion are thus eliminated-from the chamber through `the vent outlet openings 2U as the Valves (controlling s same` arev open. After completely scavenging the -furnace retort chamber of the products of combustion whichdtakes `only a short time, the valves .or closures2l are` elosedthus permitting the pressure Withinthe retort chamber to approachor attain .the sameyalue as the pressure `of the gas Within the second induction system 23. The next step is to maintain-the Iatmosphere `of predetermined analysis, and lto the regulable valve 21 is designed to admit such gases asis .needed to maintain` an atmosphere Within the retort chamber of the desired analysis and pressure.

. It -willbe apparent .that the various controls for;preparing this furnace retort chamber for subsequent operations in heat treating material maybe operated manually if so desired. However,v these various operations must be carriedout very quickly, and in order tomaintainjeicient operation Yof the'furnace, itis desirable to incorporate anautomatic means forcontrolling these successive operations Vof the furnace', and there# Y nog.

fore, in Fig. i, have illustrated one practical solution for automatically controlling the various steps in my new method of furnace operation.

I have provided a master control device B" which may be driven from any suitable source of power, and comprise principally a drive shaft 30 carrying a member 3l that carries a Contact arm 32, member 3i being electrically connected in any suitable manner to a source of electric current supply 33 through an electrical connection 34,

Whichincludes a brush 35 and switch 36 which may be opened to cut the Whole control system Preferably, suitable means are provided forcontrolling theoperation of member 3i so that same will, When put in operation, have only one complete revolution. 'I'his may be accomplished by means of any suitable mechanical or electrical mechanism which is Well known in the art; and which is here designated as a Whole by reference character 31, samebeing operated .by a lever 37a. This mechanism preferably includes a brake 38 operable to engage the brake vdrum 39 carried by member 3l so as to stop the rotation of member 3i when it has completed one revolution. The at res position is identified by character 43 and I have illustrated the contact arm 32 in the at rest position by'dotted lines in Fig. 1.

` As the mechanismV is placed in timed operation, the contact arm 32 rst engages the stationary contact ring 4| which ring is connected through the electric connection 42 to a. solenoid 43 and these by connection 44 to the source of electric power 33. The solenoid 43 operates the plunger 45 which is connected with an actuating arm 46 of thevalve I5. This valve I5 has been previously moved to the on position so that combustible fuel is fed to the furnace to beV burned for heating same, this valve being preferably turnedfof and on by a Ymanually operated arm 4l. VWhen the contactv arm 32 contacts the contactring 4i the solenoid 43 is'fenergized to retract the plunger 45 and thus move the arm '43 tothe off positionthus closing the valve `|5 and shutting off the supply of combustible fuel which is'being fed to the furnace retort Vchamberl. As thelcontrol .mechanism continues its operation the Contact arm 32'next engagesthe contact ring 50 which is connected with leads 5| and 52 leading to the solenoids 53 and 54respe ctively. Connections 55 and 56 connect theotherterminalsof the solenoidsWith-the source of electric power 33. Thus, after the fuel supply hasbeen cut off the solenoid's 53 and 54 are energized'to retract the plunger 51, which is; connected-With the arm 58 Vof the Aregulable-valve 21., Thus the ,arm 58 is moved Vfrom the off position to afi'ull on position, and the ushing gas of ,predetermined analysis and. pressure is'thus allowed, to rush through the pipe -23'or 23athrough the v intake 22 or H into-the furnace retort chamber IB. Thisgas flushes the chamber and scavenges all of the products of combustion then remaining inthe chamber through the vent outlet openings 28. It will be apparenttliatin-a short, Whilegthe retort chamber Aiscomp1etely-clearedof objectionable gases and vapors cpmprising the -products'of combustion, and my control is designed so that while valve 21- is full gon the valves; or closures 2l controllingthev vent outletopejnings are actuated to close. It will be seen that Vasthe contact arm 32 is rotatedit-willnextfengagethe contact ring 60 which isponnected vviighjtheelecfI trical connection 6| leading to the solenoid 62,

'fell wnicnis iccnneetedwi-tnan-arm @'65 andlinks 66 'with tihe valves er :closure :members 12 I y.

The rotating contactngfarm .13.2 -will InextLpass fbeyond the end of fthe contact ir-ling 25e fand fdis- @vconn'ect'fthelsolenous 153 :and "5t rrcm :the -r source of ieleetricalhpower tnroughitne :ring u. -:Preferifably 'Stn plunger 151 has associated Ltnerewith Lsxme suitable resilient VSor spring :return mean's tending to move the valve arm 58 to vlafcl'o'se'cl for You position. LBu't before :the contact :arm Aleaves the contact .ring :150 it :iis arranged .totengage .tnerccntact `ring 11:0 :is :connected :by fan electrical :connection :'Ll fwitnilmelez :connected with one terminal Io'f 'the fsolenbid 54 A.andTthus when the contact arm leaves contactringf' it cnly tnesolenoidf damn-ien `isfile-"energized and thusvthemperatieniofssolenoidrtfa alone: moves fthe plunger 51 so .as :to move Pth'e valve arm 158 4.to itlre"fpart onmposiftion im wnicnfiha's been rpredetermined :accordance iwitn A:pred'eterrrline'd :nt part Senposition l'tne `valve 21 censtructedzto supply lesser Lamount lof Nthis ned .analysis -t`0 the @furnace retort enamberiand 4prefexiablyfat1a @lesser pressuralwnienlpressure is fp'rfe'determ'inedA to sup- @ply just tne prep'ersamount ofirtnisJgas or Aprefdeter ned 4'analysis "to the furnace .-rtcrt chai-nfbe'r @for fuse finfsub'seduentfoperations fo fthe furmace neattreating fitneld'esire-d material.

EI-Zl'ie time element-for llu's'hingthechamberfand forintrbducinggaisltherto at a-'reluce'd pressure may be Lvariedlby lengthening =or shortening-the contact rngsiarrdtl las inlicateidby-thedotted lines 50a and 10a in Fig. 1. Obviously the means for-varying-theltimeintervals is preferably manually operated and the constructional details are somewhat dependent on the type of control employed.

As the contact arm continues its rotation it will complete one revolution when it reaches the at rest. position 40. In the at rest position, said contact arm moves out of contact with the contact rings 4| and 60, thus die-energizing the solenoids 43 and 62 respectively. The plungers 45 and Btl are preferably constructed so that same will not be spring returned as it is desired that the fuel valve l5 remain off and the valves 2| remain closed when the contact arm is positioned at the at rest position. The valve 21 is, however, preferably spring closed when the solenoids 53 and 54 are de-energized although if desired, the plunger 51 may be constructed Without a spring return if it is desired to continue feeding in this gas through line 23 for maintaining the proper atmosphere in the retort chamber during subsequent operations of the furnace in heat treating the selected material. Preferably, however, the contact ring is extended as at y10b and the arm 32 is still in contact therewith at the at rest position so that the valve 21 will be maintained in the part on position. Preferably line 56 embodies a switch 56a having a switch arm 55h connected with arm 46 of the fuel valve l5 so that when the fuel is turned o the switch 56a will be turned oif but turned on again as soon as valve l5 is turned oi The above control means will automatically control these successive operations consisting in first shutting olf the supply of combustible fuel, then flushing the chamber, next closing the vent openings, and finally varying the regulable valve P21 forfcontinuingtheintrnductionf of daheszflushing .gas fof a predetermined analysis ianid at da tpredetermined reduced -pressure :until :such time ias .ltnefifu'elsis again T turned on af'or mperation :of another-cycle. r

In opening 'theffurnace :door'rit will ibe apparent: that "much of ithe L-atrnospnere "within the chamber might be lost 'zbut .I find .it @truite :satisfa'etory to :provide means vassociated with :the Ad'oo'rssothat when sameisbpened thersolenoid 53 Avilllbe energized fito momentarily Yturn the :gas valve 211fullfon. Th'isis preferablyaccomplished ii'byimeansrof @plunger 80 mounted inthefurnace lwhich is urged 'Jou't'wardly by :means of:a'sp1:ing Y'8| but held :iin a Lretractve iposition `#by the ydoor 'whenssameislclosed :Asatne door is fdp'ened, :the .plungerfl iisurged outwardly of theurnace :and .is icon'nected withian 'armlf82 which is ithusmoved into vengagementwith a 'contact Contact U83 'iis `connected :by Ian-electrical -connection i313 .with one terminal df solenoid 53 lwhil'e lthe aar-111282 Sis connected with 'the source kof lelectrical `power '3'3 fby 'means of ianV electrical :connection 85 Vand the lead 34. .Thus 'when 'the .door Sis fclose'd after Aplacing the material sito Sbe :heat ftr'eated .finlthe uretort chamber secondiinduction-systemds:partly cut off as the solenoids 53 is ,de-'energized valve`21 remaining fpart.onlbecause contactfarm w32.is still inl contact Ywithffcontact:rin'glf10 'at 10b.

flIn Fig. 2, lI have .illustrated a .modi'ed Icon- -struction kwhich comprises a mechanical fcon'trol "device suitable '.fo'r controlling zth'e combustible vfuel valve .|5, .ga's Ivalve 21 Vand 'the 'valves :Torrelo- Aisure's l121|.. This lmodfed structure provides 2a motor M connected to drive a cam C through Y a speed reduc'er9`0 4byime'ans 'ofsuitablebevelled gears 19 "a trip mechanism 92.inc1uding'5a brake `bistro-e 293 :of standard l.construction :is associated "with the cam C 'to stop same rwhenxit :has fcompleted one revolution, said mechanism being constructed to also cut 01T the motor M and this mechanism can be again put into operation by moving the arm 94. Since this type of mechanism is well known in the art it is not deemed necessary to illustrate or describe the details of the structure. The cam C carries an actuating cam portion which is engaged by the plunger 96 as the roller 91 carried by said plunger 96 rides on the cam portion 95. It will open communication between the hydraulic lines 91a, through the Valve 98 and thus function to operate the valve |5 in any suitable manner so as to close said valve. Likewise, as the cam is rotated in the direction of arrow 99, the cam portion |00 is brought into engagement with roller |0| carried by plunger |02, whereby to operate valve |03 to connect the hydraulic lines |04 in such a way as to operate the atmosphere lcontrol Valve 21, cam portion |00 maintaining said Valve 21 in a full position. Next the cam portion |05 is moved into contact with roller |06 carried by plunger |01 and thus the valve |08 is operated to place the hydraulic lines |09 in communication so as to operate a suitable mechanism for closing the chamber outlet valves 2|. Subsequent to the closing of the chamber outlet valves 2|, the roller |0| leaves the cam portion |00 and rides on the cam portion lli) so as to move the valve |03 to connect the hydraulic line whereby to actuate the valve 21 in a suitable manner to move same to part on position, and to maintain the valve 21 in a part on position in the rat rest position of said mechanism.

It will thus be seen that the mechanical control means illustrated in Fig. 2 can be constructed and arranged for actuating: valves 5, 21 and 2| in a manner similar to the electrical control means illustrated in' Fig'. 1. A If desired, suitable hydraulic lines H2 may be connected with lines |04 and with a suitable valve which is actuated by opening the furnace door 25 so as to momentarily open valve 21 to a full on position when the furnace door is open. Y

lIt will be understood that the time element involved in completing the cycle of operations necessary in preparing the furnace retort chamber for subsequent operations in the heat treatment oi. ferrous alloys or other material may be conveniently varied, the regulable valve 21 may be constructed and arranged-so same can vbe ad- J'ustedwithin limits, so as to make it possible to very accurately control the atmosphere Within the furnace when heat treating said material. It will be obvious that the incorporation of an automatic control makes the operationvof the furnace substantially fool proof and this controlV means and method is particularly important when heat treating materials subjected to a high heat in a controlled atmosphere'in the process ofV heat rtreating same, especially when employing a. process embodying a positive time and temperature control.

` `The principles of my invention are of par- Aticular utility in connection with the heat treatmentor' materials ina furnacev of the gas fire type, ,and the operation of my process for preparing and maintaining an atmosphere of predetermined analysis and pressure in a furnace of .this type is found to be of great importance and utility.

In the treatment of some materials it is de'- sired to employ an inert atmosphere in the fur- Vnace retort chamber such as N2 gas and the valve 21 is capable of controlling the pressure of this inert gas.` In other applications it is found desirable to employ a carburizing gas atmosphere such as CO or other carburizing gases, and thus the mechanism herein illustrated and described is applicable for supplying and maintaining by means of the regulable valve 21 suchan atmosphere inthe furnace retort chamber.

The mechanism and method described herein may be manually controlled but is preferably automatically controlled by some suitable electrical or mechanical means such as is typied by the constructions illustrated in the accompanying drawings.

It will be apparent to those skilled in the art to which my invention pertains, that various modications and changes may be made therein without departing from the spirit of my invention or from the scope of the appended claim.

I claim: i

The combination with a heat treating furnace having a retort chamber adapted to receive material to be treated, and a door opening into said chamber, of means for introducing a heating medium into said chamber, valve means for controlling the iiow of said heating medium through said introducing means, means for introducing a non-oxidizing gas into said chamber, a second Valve means for controlling the flow of said gas through the second mentioned introducing means, actuating means connected to both said valve means, and a common control means for said actuating means operable to effect actuation of said valve means in timed relation to each other, said control means being so constructed and arranged as to cause closing of the first mentioned valve means as a condition precedent to the opening of said second valve.

FREDERICK A. ENDRES S. 

